This invention relates generally to measuring preselected attributes of process fluids and slurries. More specifically, this invention is particularly suitable for, but not limited to, the in-line measurement and monitoring of the pH of fluids and slurries used in oil field operations.
Currently, various oil field services require that liquids and slurries that are to be injected into the well bore have pH values within a specific pH range. Furthermore, as well-treatments become more complex, it is becoming essential that the formulated liquids and slurries to be used in the treatment have a pH within a very narrow range to ensure the successful treatment of the well. Thus, pH measuring of liquids and slurries must be accurate, reliable, and to ensure the best results, capable of being performed while the liquids and slurries are being pumped into, or about the well.
Historically, the pH of a liquid, or slurry, has been monitored by obtaining a sample of the liquid, or slurry, and submerging a pH indication tape or an electronic probe sensor into the sample. In the case of using a probe, the probe generates an electrical signal that is converted into meaningful pH values by an appropriate electronic processor and those values are displayed on a meter, charted, or otherwise recorded. In order to calibrate the probe sensor, at least one, and preferably two buffer solutions having known but different pHs must be kept on hand. The probe sensor calibration process includes checking and tuning the electronic processor to display the desired value for each buffer solution. For example, if a selected calibration solution has a pH of 7, the processor would be adjusted to display the value of 7 indicating a neutral pH. The probe sensor could then be subjected to a second buffer solution having a different pH and the processor again adjusted to display the correct value. The calibration steps are repeated as necessary to ensure that the monitoring system is properly calibrated. Additionally, the probe sensor, when not in use, must be kept submerged in an aqueous solution to prevent the sensor from drying and thus permanently damaging the probe sensor.
The above procedures are not difficult to perform in a laboratory environment, however, the procedures can be very difficult to perform in conditions typically found in the field, such as extreme heat and cold, high winds, dust, rain, and snow, etc.
Therefore, there remains a need within the art for measuring/calibration/probe storage apparatus that provides an effective and convenient system to measure selected attributes of liquids and slurries, such as the pH thereof, in adverse conditions as well as a need for an apparatus that provides a means for storing probes for extended periods of time in such conditions.
There also remains a need within the art for measuring/calibration/probe storage apparatus that is capable of measuring selected attributes such as the pH of a liquid, or slurry, while such liquid, or slurry is in transit to the well bore, often referred to as being "on-line".
There is a further need within the art for measuring/calibration/probe storage apparatus which allows for the calibration and installation of a replacement probe without disturbing the well treatment operation.
These and other needs within the art are met by the invention disclosed herein.